Tanzanite is called after the East African state of Tanzania, it was discovered in the Mererani Hills of Northern Tanzania in 1967. Tanzanite is trichroic i.e when light enters it appear alternately sapphire blue, violet and burgundy. Tanzanite is usually a reddish brown in its rough state. Heating occurring underground naturally or in a furnace removes the brown or burgundy color. Tanzanite becomes dichroic when heated; its colour changes blue-purple to purple-blue. Some of the tanzanite is applied with a layer containing cobalt, to improve the color.
Mohs hardness :- 6.5